I have that code:

...
  request data = new request(); 
  data.username = formNick; 
  xml = data.Serialize();
...
[System.Serializable] 
public class request 
{ 
   public string username; 
   public string password;

   static XmlSerializer serializer = new XmlSerializer(typeof(request));
   public string Serialize() 
   { 
      StringBuilder builder = new StringBuilder(); 
      XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
settings.Encoding = Encoding.UTF8;
      serializer.Serialize(
         System.Xml.XmlWriter.Create(builder, settings ), 
         this); 

      return builder.ToString(); 
   } 
   public static request Deserialize(string serializedData) 
   { 
      return serializer.Deserialize(new StringReader(serializedData)) as request; 
   } 
}

I want to add attributes to some nodes and create some sub-nodes. Also how to parse xml like that:

<answer>
  <player id="2">
    <coordinate axis="x"></coordinate>
    <coordinate axis="y"></coordinate>
    <coordinate axis="z"></coordinate>
    <action name="nothing"></action>
  </player>
  <player id="3">
    <coordinate axis="x"></coordinate>
    <coordinate axis="y"></coordinate>
    <coordinate axis="z"></coordinate>
    <action name="boom">
      <1>1</1>
      <2>2</2>
    </action>
  </player>
</answer>

p.s. it is not a xml file, it's answer from http server.